The present invention relates to a mechanism for selectively producing fast response, intermittent rotary motion under the control of low power, digital signals and more particularly, for such apparatus when applied to manipulate a workpiece in a sewing machine.
In the field of automatically guiding fabric material as it is mechanically passed through a sewing machine, there are numerous prior art devices. Most of these devices are completely incapable of keeping up with present day high-speed sewing machines because of inertia problems. The actual manipulative device for the fabric workpieces must be capable of extremely fast acceleration and deceleration; therefore, it must be of a relatively low mass. In some prior art guiding devices, a rotatable guide is used ahead of the sewing machine needle. See, for example, U.S. Pat. No. 4,019,447 (Blessing, et al.) and U.S. Pat. No. 3,650,229 (Rovin). In the Rovin device, the guide is reciprocated up and down with the needle. Since the guide is relatively heavy, it can be appreciated that the acceleration and deceleration of the guide requires great force or a relatively low sewing rate. The device described in the Blessing patent does not utilize such reciprocation, but instead uses a low mass guide wheel. Unfortunately, this device does not have the feature that enables the fabric to be selectively manipulated either when the needle is down or when the needle is up. Manipulation of the fabric takes place regardless of the position of the needle.
Similar problems occur in other automated garment manufacturing devices where it is desired that some rotary motion take place in synchrony with a reciprocating motion, but that it only take place at intervals which can be selected under the control of low power digital, electrical signals. Heretofore, there have been no prior art devices which could provide such fast response control for relatively high powered rotary drives.